Sometimes finding a skeleton in a closet can be a good thing – if you’re a paleontologist. Meet Pelagornis sandersi, a giant bird with a wingspan 21 feet across – so wide that it could have been the size of a (very) small plane.

The one and only known Pelagornis sandersi fossil’s wings stretch a whopping 6.4 meters (or 20.99 feet) – about twice that of the royal albatross, among the largest living birds capable of taking to the skies. It sported strange tooth-like cones that protruded from its beak. The remarkable bones were actually discovered in 1983 near Charleston Airport in South Carolina, but they remained hidden in a drawer at the Charleston Museum until study author Daniel Ksepka, a paleontologist then at North Carolina State University in Raleigh, came across them about three decades later.

The stupid thing is the scientist said it, "The larger the bird, the harder it is for the muscles to lift the weight so it could fly." Likely scenario here, this is the largest "Possible" flying bird, but doesn't because it is too big and heavy. I am sure the younger of...

“I was not expecting this bird when I went down there,” said Ksepka, now at the Bruce Museum in Connecticut. Ksepka named the strange specimen after Albert Sanders, the now-retired curator who collected the unique fossil after it was discovered — and who later invited Ksepka to come look through fossils at the museum.

P. sandersi, which probably lived 25 million to 28 million years ago, was probably larger even than another extinct mega-bird, Argentavis magnificens, Ksepka said. Some have previously estimated that Argentavis’ wingspan was nearly 7 meters, but Ksepka said with the data in hand, Pelagornis still wins: Argentavis would have had a size range of 5.09 to 6.07 meters and Pelagornis would have been about a meter longer, at 6.06 to 7.38 meters. (Argentavis was probably more massive, however.)

Birds come in all sizes – and some species that have cropped up over the last 150 million years have been a thousand times larger than their brethren. But there’s a cost. As a bird gets heavier, it becomes harder and harder for its muscles to propel the bird up and away. This means there must be a natural limit – and if scientists weren’t able to study the fossil record, they might be tricked into thinking that the wide-winged albatross sat near that upper limit.

But the skeletons of long-gone fliers like Pelagornis shows that it must be possible. Ksepka thinks it’s partly due to the bird’s shape, because it had extra long wings compared to its relatively small body. This old bird could probably have glided at a decent clip, around 39 miles per hour.

The findings “raise the ceiling for birds — we increase the upper limit of how large we knew birds could get in terms of wingspan,” Ksepka said. “It’s just another example where the fossil record can tell us something about biology that we might not be able to know from what we have around today.”

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